1. Field of the Invention
The present invention relates to an electrophotographic photoconductor, and more particularly to a panchromatic electrophotographic photoconductor which exhibits remarkably high photosensitivity in a broad wave range from the visible region extending to the near infrared region.
2. Discussion of Background
Inorganic materials such as Se, CdS and ZnO are conventionally employed as the photoconductive materials for use in an electrophotographic photoconductor. However, because of poor photosensitivity, low thermal stability, and toxicity of the inorganic photoconductors, electrophotographic photoconductors using organic photoconductive materials have been actively developed in recent years. Some organic photoconductors, which comprises a photoconductive layer containing a charge generating material and a charge transporting material are put to practical use.
The electrophotographic photoconductor is required to exhibit spectral sensitivity in a broad wave range from the visible region extending to the near infrared region to use in a variety of electrophotographic apparatuses which employ a semiconductor laser beam as a light source, such as a laser printer and a digital copying machine, and to cope with various kinds of light source employed for exposure system in such apparatuses.
It is proposed to use in the photoconductor two or more kinds of pigments serving as the charge generating materials which exhibit spectral sensitivities in different ranges, as disclosed in Japanese Laid-Open Patent Applications Nos. 63-148264, 1-17753 and 1-270060.
However, the sensitivities of the photoconductor thus obtained are not flat in a broad wave range due to local decrease, and do not attain to a sufficient level as a whole although the spectral range in which the photoconductor can show the spectral sensitivity expands. In addition, the characteristics of the pigments cannot be effectively utilized in such a photoconductor.